Meta-analysis to estimate the load of Leptospira excreted in urine: beyond rats as important sources of transmission in low-income rural communities

Leptospirosis in India: insights on circulating serovars, research lacunae and proposed strategies to control through one health approach

Leptospirosis is one of the most neglected zoonotic infections of public health concern worldwide and a remerging infection in tropical countries such as India. The infection least explored disease and the epidemiological and other critical data are scarce for the disease rate reported and to control the infection. Leptospirosis as sapronosis is as underrated as the infection itself, and this article aims to explore the significance of this aspect of the disease. The research review aimed at the epidemiological understanding of the infection to control the negative impact of the disease. A mixed review and analysis were carried out to understand the knowledge published on the critical and understudied areas like epidemiology, transmission, diagnosis, treatment, and control of infection. A systematic analysis was carried out to extract information about the reported circulating strains, and research lacunae in India with the published data available in PubMed. The article elaborately discusses crucial inference areas of infection transmission and addresses lacunae in critically unacclaimed areas of infection to control the spread of infection using one health approach (OHA), and strategies to control leptospiral infection are proposed. The article also reviewed how and why Leptospirosis can be best studied and controlled by "One health approach" in India.

Domestic dogs in indigenous Amazonian communities: Key players in Leptospira cycling and transmission?

BACKGROUND

Leptospirosis is the world's most common zoonotic disease. Mitigation and control rely on pathogen identification and understanding the roles of potential reservoirs in cycling and transmission. Underreporting and misdiagnosis obscure the magnitude of the problem and confound efforts to understand key epidemiological components. Difficulties in culturing hamper the use of serological diagnostics and delay the development of DNA detection methods. As a result, especially in complex ecosystems, we know very little about the importance of different mammalian host species in cycling and transmission to humans.

METHODOLOGY/PRINCIPAL FINDINGS

We sampled dogs from five indigenous Kichwa communities living in the Yasuní National Park in the Ecuadorian Amazon basin. Blood and urine samples from domestic dogs were collected to assess the exposure of these animals to Leptospira and to identify the circulating species. Microscopic Agglutination Tests with a panel of 22 different serovars showed anti-leptospira antibodies in 36 sampled dogs (75%), and 7 serogroups were detected. Two DNA-based detection assays revealed pathogenic Leptospira DNA in 18 of 19 dog urine samples (94.7%). Amplicon sequencing and phylogenetic analysis of 16S rRNA and SecY genes from 15 urine samples revealed genetic diversity within two of three different Leptospira species: noguchii (n = 7), santarosai (n = 7), and interrogans (n = 1).

CONCLUSIONS/SIGNIFICANCE

The high prevalence of antibodies and Leptospira DNA provides strong evidence for high rates of past and current infections. Such high prevalence has not been previously reported for dogs. These dogs live in the peridomestic environment in close contact with humans, yet they are free-ranging animals that interact with wildlife. This complex web of interactions may explain the diverse types of pathogenic Leptospira observed in this study. Our results suggest that domestic dogs are likely to play an important role in the cycling and transmission of Leptospira. Future studies in areas with complex ecoepidemiology will enable better parsing of the significance of genotypic, environmental, and host characteristics.

A Cross Sectional Study on the Bidirectional Interactions Between Leptospirosis and HIV Infection Among Patients from Maputo Central Hospital, Mozambique

Introduction

This study aims to determine the baseline seroprevalence of leptospirosis, a zoonotic and neglected disease, in people living with HIV (PWH) in Maputo, Mozambique, and to evaluate the relationship between selected HIV-related factors that might influence risk of coinfection with leptospirosis, such as degree of immunosuppression, as assessed by CD4 cell count, World Health Organization (WHO) HIV/AIDS clinical stage and antiretroviral therapy (ART) intake.

Methods

This was a descriptive cross-sectional analysis of 157 PWH, aged over 18 years old, admitted to the Maputo Central Hospital, in Maputo, Mozambique, between March 2020 and October 2021. The study participants were recruited as a convenience sample regardless of the reasons for their admission. We collected sociodemographic and clinical data, including ART and WHO HIV/AIDS clinical stage, and blood for CD4 cell count and detection of Leptospira IgG antibodies using a commercial Kit ab247199 Leptospira IgG ELISA (www.abcam.com/ab247199) with sensitivity and specificity of 100% and 97.3%, respectively. Laboratory testing was performed at the Faculty of Medicine, Eduardo Mondlane University and Laboratory of Clinical Analysis, in Maputo.

Results

Participants were aged 18 to 72 years (median age 39 years; SD ± 10.5), the majority were female 100 (63.7%), from urban areas 138 (87.9%), with secondary-level education 80 (51%). The overall seroprevalence of Leptospira IgG antibodies was 40.1%. The median CD4 cell count was 385 cells/µl (02 to 2297; SD ± 378.47). Higher seroprevalence of Leptospira antibodies was found among participants with CD4 cell counts <250 cells/µl (54.8%), WHO HIV/AIDS stage IV (70.2%) and those on ART (92%), though there were no statistically significant differences between groups with and without Leptospira antibodies.

Conclusion

Our study confirmed that Leptospira antibodies are highly prevalent in PWH in Maputo; however, Leptospira infection was not associated with the degree of immunosuppression, WHO HIV/AIDS clinical stage, or the use of ART. Our data support the need for routine screening for leptospirosis in PWH in Mozambique. Future studies are warranted to characterize the incidence and outcomes of symptomatic leptospirosis in this patient population and to identify circulating serovars and species in the country and region, as well as the implicated reservoirs.

Leptospirosis and the Environment: A Review and Future Directions

Leptospirosis is a zoonotic disease of global importance with significant morbidity and mortality. However, the disease is frequently overlooked and underdiagnosed, leading to uncertainty of the true scale and severity of the disease. A neglected tropical disease, leptospirosis disproportionately impacts disadvantaged socioeconomic communities most vulnerable to outbreaks of zoonotic disease, due to contact with infectious animals and contaminated soils and waters. With growing evidence that Leptospira survives, persists, and reproduces in the environment, this paper reviews the current understanding of the pathogen in the environment and highlights the unknowns that are most important for future study. Through a systematic Boolean review of the literature, our study finds that detailed field-based study of Leptospira prevalence, survival, and transmission in natural waters and soils is lacking from the current literature. This review identified a strong need for assessment of physical characteristics and biogeochemical processes that support long-term viability of Leptospira in the environment followed by epidemiological assessment of the transmission and movement of the same strains of Leptospira in the present wildlife and livestock as the first steps in improving our understanding of the environmental stage of the leptospirosis transmission cycle.

Urine shedding patterns of pathogenic Leptospira spp. in dairy cows

Pathogenic Leptospira spp. are zoonotic bacteria that infect wild and domestic animals. Humans contract leptospirosis directly through contact with infected animals or indirectly from contaminated water or soil. In mammalian reservoirs, the pathogen can colonize renal tubules for lengthy periods and persistently contaminate the environment through urine. Cattle have been reported to shed several serovars; with Hardjo the most common serovar found in cattle. Without clinical manifestations, the infection can spread within a herd, impairing productivity, and putting workers like farmers, abattoir operators and veterinarians at risk. The dynamics of pathogenic Leptospira shedding was studied in six dairy herds in southern Chile. Various intermittent urine shedding patterns were found, with elimination periods between 79 and 259 days and bacterial loads ranging from 3 × 10⁴ to 4.4 × 10⁴ bacteria/mL. The current study was the first to assess the various urine shedding patterns and loads of pathogenic leptospires shed through urine of naturally-infected dairy cows. In addition, the study suggests that vaccination does not prevent cattle infection, although it influences loads of pathogenic leptospires excreted in urine. Our study provides a great awareness of asymptomatic animal carriers in an endemic area and will contribute to improving disease control and designing better prevention strategies.

Effects of Diazinon Exposure on Urinary Shedding of Leptospira interrogans Serogroup Hebdomadis in Mice

Wild rodents are natural hosts of Leptospira spp. and are exposed to various pesticides, some of which are immunotoxic. Rodent urine is an important source of infection for humans and other animals. We evaluated the effects of pesticide exposure on Leptospira growth in mice. Diazinon, at doses of 0.2, 1, and 5 mg/kg/day, was orally administered continuously to mice infected with Leptospira interrogans serogroup Hebdomadis for 32 days. The numbers of L. interrogans in urine and kidney tissues were significantly lower in mice exposed to 5 mg/kg/day diazinon than in unexposed mice (p < 0.05). The urinary concentration of 2-isopropyl-6-methyl-4-pyrimidinol, the metabolite of diazinon, was comparable with the concentration at which viability of L. interrogans was decreased in in vitro assay, suggesting that it had toxic effects on L. interrogans in the proximal renal tubules. Diazinon exposure reinforced Leptospira-induced expression of inflammatory cytokine genes in kidney tissues, and an enhanced immune system might suppress Leptospira growth. These results suggest that diazinon exposure may not increase the risk of Leptospira transmission to humans through mice. This novel study evaluated the relationship between pesticide exposure and Leptospira infection in mice, and the results could be useful for risk assessment of leptospirosis.

Diagnostic accuracy of an immunomagnetic separation-PCR assay to detect pathogenic Leptospira spp. in urine from dairy cattle, using a Bayesian latent class model

Leptospirosis is a zoonotic disease that has spread worldwide and causes significant economic losses in the dairy industry. The causal agents of this infectious disease are members of the genus Leptospira, known as pathogenic Leptospira spp. Specific clinical signs of the infection are difficult to detect. Therefore, the disease is normally under-diagnosed, mostly due to the lack of a cost-effective technique for diagnosing animals with a low bacterial load in their urine. The aim of this study was to assess the diagnostic accuracy of a qPCR coupled with a previous Immunomagnetic separation (IMS) step (IMS-qPCR) against a qPCR without using IMS, using a Bayesian latent class model (2 tests, 3 populations) to determine the leptospirosis infectious status in naturally infected dairy cattle. The results revealed that IMS qPCR had a sensitivity (Se) of 95.7% (95% Probability Interval (PI) = 85.0; 99.4%) and a specificity (Sp) of 98% (95% PI = 96.1; 99.4%), indicating that it is more sensitive than conventional qPCR (Se = 69.7% (95% PI = 59.2; 79.0%); median difference = 25.2% (Monte Carlo Error = 10.2%); and the Sp = 98.8% (95% PI = 97.6; 99.5%), median difference = 0.8% (Monte Carlo Error = 2.1%). Therefore, results shows that IMS-qPCR is a more useful diagnostic tool in terms of accuracy for detecting infectious animals with pathogenic Leptospira in their urine.

Leptospirosis in Ecuador: Current Status and Future Prospects

The location of Ecuador-an equatorial nation-favors the multiplication and dispersal of the Leptospira genus both on the Pacific Coast and in the Amazon tropical ecoregions. Nevertheless, leptospirosis epidemiology has not been fully addressed, even though the disease has been recognized as a significant public health problem in the country. The purpose of this literature review is to update knowledge on the epidemiology and geographical distribution of Leptospira spp. and leptospirosis in Ecuador to target future research and develop a national control strategy. A retrospective literature search using five international, regional, and national databases on Leptospira and leptospirosis including humans, animals, and environmental isolations of the bacteria and the disease incidence in Ecuador published between 1919 and 2022 (103 years) with no restriction on language or publication date was performed. We found and analyzed 47 publications including 22 of humans, 19 of animals, and two of the environments; three of these covered more than one of these topics, and one covered all three (i.e., One Health). Most (60%) of the studies were conducted in the Coastal ecoregion. Twenty-four (51%) were published in international journals, and 27 (57%) were in Spanish. A total of 7342 human and 6314 other animal cases were studied. Leptospirosis was a frequent cause of acute undifferentiated febrile illness in the Coast and Amazon and was associated with rainfall. All three major clusters of Leptospira-pathogenic, intermediate, and saprophytic-were identified from both healthy and febrile humans, the environment, and animals; moreover, nine species and 29 serovars were recorded over the three Ecuadorian ecoregions. Leptospira infections were diagnosed in livestock, companion, and wild animals from the Amazon and the Coast regions along with sea lions from the Galápagos Islands. Microscopic-agglutination test was the diagnostic tool most widely used. Three reviews covering national data on outpatients and inpatients determined the varied annual incidence and mortality rate, with males being more commonly affected. No human cases have been reported in the Galápagos Islands. Genomic sequences of three pathogenic Leptospira were reported. No studies on clinical ground, antibiotic resistance, or treatment were reported, nor were control programs or clinical-practice guidelines found. The published literature demonstrated that leptospirosis was and still is an endemic disease with active transmission in the four geoclimatic regions of Ecuador including the Galápagos Islands. Animal infections, distributed in mainland and insular Ecuador, pose a significant health risk for humans. Nationwide epidemiological surveys-encouraging more research on the fauna and environment with appropriate sampling design on risk factors for human and animal leptospirosis, Leptospira genotyping, increased laboratory capability, and readily available official data-are required to improve our understanding of transmission patterns and to develop effective national intervention strategies with the intention of applying One Health approaches.

Leptospira Infection in Rural Areas of Urabá Region, Colombia: A Prospective Study

The objective of this study was to analyze the eco-epidemiological aspects of Leptospira seroprevalence and seroincidence and its associated factors in two municipalities of northwest Colombia. A prospective study was performed in rural areas of Urabá, Antioquia, Colombia. The study enrolled 597 people between November 2015 and January 2016, of which 274 were followed up 1 year later. Serologic testing was performed by a microscopic agglutination. The outcomes were seroprevalent and seroincident cases, and the primary exposure was an outdoor occupation. A binary and mixed-effect multinomial logistic regression model was used to estimate factors associated with seroprevalent or seroincident cases of Leptospira infection. The overall Leptospira seroprevalence was 27.81% (95% confidence interval: 23.62-32.49), and the overall cumulative seroincidence for Leptospira was 14.60% (95% confidence interval: 10.33-20.23). Multivariable analysis showed that factors associated with L. interrogans serogroups seropositivity were outdoor occupation, male gender, older age, the presence of dirt floor in the household, and the presence of piglets and opossums. It also showed that factors associated with other Leptospira species serogroups were the presence of pit latrines and of turkeys. In addition, the multivariable model of seroincident cases of L. interrogans serogroups evidenced outdoor occupations, the presence of rats, and corn cultivation as risk factors. Likewise, the multivariable model for seroincident cases of other Leptospira species showed that the presence of hunting canines and cassava cultivation were risk factors. We found specific factors associated with the transmission of Leptospira serogroups contribute to the understanding of the epidemiology of Leptospira infection in rural areas of Urabá, Colombia.

Leptospiral sphingomyelinase Sph2 as a potential biomarker for diagnosis of leptospirosis

Leptospirosis is an underestimated infectious tropical disease caused by the spirochetes belonging to the genus Leptospira. Leptospirosis is grossly underdiagnosed due to its myriad symptoms, varying from mild febrile illness to severe haemorrhage. Laboratory tests for leptospirosis is an extremely important and potent way for disease diagnosis, as the clinical manifestations are very similar to other febrile diseases. Currently available diagnostic techniques are time-consuming, require expertise and sophisticated instruments, and cannot identify the disease at an early phase of infection. Early diagnosis of leptospirosis is the need of the hour while considering the severe complications after the infection and the rate of mortality after misdiagnosis. Secretion of Leptospira-specific sphingomyelinases in leptospirosis patient's urine within a few days of the onset of infection is quite common and is a virulence factor present only in pathogenic Leptospira species. Herein, the structural and functional importance of leptospiral sphingomyelinase Sph2 in leptospirosis pathogenesis, as well as the potential of screening urinary Sph2 for diagnosis and the scope for developing a rapid and easily affordable point-of-care test for urinary leptospiral sphingomyelinase Sph2 as an alternative to current diagnostic methods are discussed.

Long-Term Outcome of Leptospirosis Infection with Acute Kidney Injury

Acute kidney injury (AKI) is associated with long-term mortality and morbidity outcomes. Severe leptospirosis usually results in AKI and multiple organ failure, but is associated with favorable short-term outcomes, if treatment is initiated early. However, information on long-term outcomes after leptospirosis-associated AKI is limited. The effects of leptospirosis on resulting chronic kidney disease (CKD), as well as mortality, were evaluated in this study. We studied 2145 patients with leptospirosis from the National Health Insurance Research Database over an 8-year follow-up period. Patient demographics and characteristics were analyzed for AKI and dialysis. The risk factors for renal outcomes were analyzed using multivariate logistic regression. In total, 443 (20.6%) patients had AKI. Among them, 77 (3.6%) patients received replacement therapy (AKI-RRT group). Long-term mortality was higher in the AKI-RRT group than in the AKI group and non-AKI group, based on a multivariate logistic regression model. Similarly, the incidence rate of CKD was highest in the AKI-RRT group, followed by the AKI and non-AKI groups. Leptospirosis, complicated with AKI, may play a critical role in the long-term outcomes, resulting in CKD. The severity of AKI determines the incidence of CKD. Additional prospective investigations for the early detection of AKI in leptospirosis are warranted.

A global one health perspective on leptospirosis in humans and animals

Leptospirosis is a quintessential one health disease of humans and animals caused by pathogenic spirochetes of the genus Leptospira. Intra- and interspecies transmission is dependent on 1) reservoir host animals in which organisms replicate and are shed in urine over long periods of time, 2) the persistence of spirochetes in the environment, and 3) subsequent human-animal-environmental interactions. The combination of increased flooding events due to climate change, changes in human-animal-environmental interactions as a result of the pandemic that favor a rise in the incidence of leptospirosis, and under-recognition of leptospirosis because of nonspecific clinical signs and severe signs that resemble COVID-19 represents a "perfect storm" for resurgence of leptospirosis in people and domestic animals. Although often considered a disease that occurs in warm, humid climates with high annual rainfall, pathogenic Leptospira spp have recently been associated with disease in animals and humans that reside in semiarid regions like the southwestern US and have impacted humans that have a wide spectrum of socioeconomic backgrounds. Therefore, it is critical that physicians, veterinarians, and public health experts maintain a high index of suspicion for the disease regardless of geographic and socioeconomic circumstances and work together to understand outbreaks and implement appropriate control measures. Over the last decade, major strides have been made in our understanding of the disease because of improvements in diagnostic tests, molecular epidemiologic tools, educational efforts on preventive measures, and vaccines. These novel approaches are highlighted in the companion Currents in One Health by Sykes et al, AJVR, September 2022.

Of Mice, Cattle, and Men: A Review of the Eco-Epidemiology of Leptospira borgpetersenii Serovar Ballum

In New Zealand (NZ), leptospirosis is a mostly occupational zoonosis, with >66% of the recently notified cases being farm or abattoir workers. Livestock species independently maintain Leptospira borgpetersenii serovar Hardjo and L. interrogans serovar Pomona, and both are included in livestock vaccines. The increasing importance in human cases of Ballum, a serovar associated with wildlife, suggests that wildlife may be an overlooked source of infection. Livestock could also act as bridge hosts for humans. Drawing from disease ecology frameworks, we chose five barriers to include in this review based on the hypothesis that cattle act as bridge hosts for Ballum. Using a narrative methodology, we collated published studies pertaining to (a) the distribution and abundance of potential wild maintenance hosts of Ballum, (b) the infection dynamics (prevalence and pathogenesis) in those same hosts, (c) Ballum shedding and survival in the environment, (d) the exposure and competency of cattle as a potential bridge host, and (e) exposure for humans as a target host of Ballum. Mice (Mus musculus), rats (Rattus rattus, R. norvegicus) and hedgehogs (Erinaceus europaeus) were suspected as maintenance hosts of Ballum in NZ in studies conducted in the 1970s–1980s. These introduced species are distributed throughout NZ, and are present on pastures. The role of other wildlife in Ballum (and more broadly Leptospira) transmission remains poorly defined, and has not been thoroughly investigated in NZ. The experimental and natural Ballum infection of cattle suggest a low pathogenicity and the possibility of shedding. The seroprevalence in cattle appears higher in recent serosurveys (3 to 14%) compared with studies from the 1970s (0 to 3%). This review identifies gaps in the knowledge of Ballum, and highlights cattle as a potential spillover host. Further studies are required to ascertain the role that wild and domestic species may play in the eco-epidemiology of Ballum in order to understand its survival in the environment, and to inform control strategies.

Risk Factors for Hospitalisation amongst Leptospirosis Patients in New Zealand

Leptospirosis is a neglected zoonotic disease that is widespread in tropical and subtropical regions such as Oceania, which includes New Zealand. The incidence rate of leptospirosis in New Zealand remains high in comparison to other high-income countries, with over half of the notified patients hospitalised, and the factors associated with hospitalisation are poorly understood. This study aimed to estimate the risk factors for hospitalisation amongst leptospirosis patients using passive surveillance data: notifications from 1 January 1999 to 31 December 2017 extracted from New Zealand’s notifiable disease database. There were 771 hospitalised and 673 non-hospitalised patients. Multivariable logistic regression was used to identify risk factors. The year of notification was significantly and positively associated with hospitalisation, with adjusted (adj.) OR 1.03 (95% CI:1.01–1.05). Occupation was significantly associated with hospitalisation, with the adjusted odds of hospitalisation amongst dairy farmers notified with leptospirosis at adj. OR 1.44 (95% CI: 1.02–2.02) times the adjusted odds of hospitalisation amongst farmers that worked with other livestock. Seropositivity for Leptospira interrogans Copenhageni (adj. OR 5.96, 95% CI: 1.68–21.17) and Pomona (adj. OR 1.14, 95% CI: 0.74–1.74)) was more likely to result in hospitalisation when compared to Leptospira borgpetersenii Ballum (baseline). Seropositivity for Leptospira borgpetersenii Hardjo (adj. OR 0.71, 95% CI: 0.49–1.01) and Tarassovi (adj. OR 0.39, 95% CI: 0.23–0.66) was less likely to result in hospitalisation when compared to Ballum (baseline). All the estimates were additionally adjusted for the effect of sex, age, ethnicity, reported occupational exposure, geographical location, reported season, and deprivation status Although passive surveillance data has limitations we have been able to identify that the New Zealand dairy farming population may benefit from a targeted awareness campaign.

Agro-Environmental Determinants of Leptospirosis: A Retrospective Spatiotemporal Analysis (2004-2014) in Mahasarakham Province (Thailand)

Leptospirosis has been recognized as a major public health concern in Thailand following dramatic outbreaks. We analyzed human leptospirosis incidence between 2004 and 2014 in Mahasarakham province, Northeastern Thailand, in order to identify the agronomical and environmental factors likely to explain incidence at the level of 133 sub-districts and 1982 villages of the province. We performed general additive modeling (GAM) in order to take the spatial-temporal epidemiological dynamics into account. The results of GAM analyses showed that the average slope, population size, pig density, cow density and flood cover were significantly associated with leptospirosis occurrence in a district. Our results stress the importance of livestock favoring leptospirosis transmission to humans and suggest that prevention and control of leptospirosis need strong intersectoral collaboration between the public health, the livestock department and local communities. More specifically, such collaboration should integrate leptospirosis surveillance in both public and animal health for a better control of diseases in livestock while promoting public health prevention as encouraged by the One Health approach.

Influence of Selective Agents (EMJH-STAFF), Sample Filtration and pH on Leptospira interrogans Serovar Icterohaemorrhagiae Cultivation and Isolation from Swine Urine

Leptospira spp. cause the zoonotic disease leptospirosis, which occurs in numerous mammalians worldwide. Isolation is still important for serotyping and genotyping of Leptospira, which in turn is essential for epidemiological surveillance of leptospirosis and the development of diagnostic tests and vaccines. However, isolation of Leptospira from clinical specimens is inherently insensitive. This study was conducted to examine the influence of selective agents, sample filtration, sample pH and the use of phosphate buffered saline (PBS) buffer for sample storage to improve the success of cultivation and isolation of Leptospira interrogans serovar Icterohaemorrhagiae from swine urine. EMJH (Ellinghausen McCullough, Johnson and Harris) medium including the selective agents sulfamethoxazole, trimethoprim, amphotericin, fosfomycin and 5-fluorouracil (STAFF) increased the success of Leptospira isolation from spiked swine urine samples. Sample filtration yielded only negative results. Isolation in EMJH-STAFF was successful from swine urine with a density as low as 10⁴ Leptospira/mL, and urine with pH ≤ 7 impaired the cultivation rate. Cultivation and isolation were not improved by the addition of PBS to spiked urine samples prior to storage for 24 h at 4 °C. The results of the study demonstrate that cultivation and isolation of leptospires from swine urine can be improved by enhanced methods.

Identification of Leptospira spp. in the animal-environment interface (swine-water) in pig production cycle

INTRODUCTION

Leptospirosis, caused by Leptospira spp., is a zoonosis with multiple hosts and reservoirs. Thus, the "One Health" approach must be addressed in order to guide prevention and control measures regarding this microorganism. There are few studies involving all stages of the pig production cycle and potential sources of infection such as water sources, which could represent a risk for local rural communities.

OBJECTIVE

To identify Leptospira spp. in the animal-environment interface (swine-water) in the pig production cycle.

MATERIALS AND METHODS

The study was conducted in a swine farm in Puerto López in the department of Meta, Colombia. Swine blood samples (n = 65) were collected for microscopic agglutination test (MAT), while urine and water samples (n = 80) were tested for Leptospira using bacterial isolation, serotyping of the isolates, and polymerase chain reaction (PCR).

RESULTS

A total of 58 (89.2%) porcine sera were positive for at least one Leptospira serogroup, with Grippotyphosa as the most frequent serogroup. Leptospira spp. were isolated in 25% (20/80) of the urine and water samples. Leptospira-positive cultures were 100% (20/20) identified within the genus Leptospira (rrl gene) and 50% (10/20) corresponded to pathogenic species (lipL32 gene) by PCR, and 45% (9/20) were positive to at least one antiserum. None of the direct urine and water samples was positive by PCR.

CONCLUSION

It is suggested that the bacteria might be transmitted in the animal-environment interface in the pig production cycle.

Amplification of pathogenic Leptospira infection with greater abundance and co-occurrence of rodent hosts across a counter-urbanizing landscape

Land use change can elevate disease risk by creating conditions beneficial to species that carry zoonotic pathogens. Observations of concordant global trends in increased pathogen prevalence or disease incidence and landscape change have generated concerns that urbanization could increase transmission risk of some pathogens. Yet host-pathogen relationships underlying transmission risk have not been well characterized within cities, even where contact between humans and species capable of transmitting pathogens of concern occurs. We addressed this deficit by testing the hypothesis that areas in cities experiencing greater population loss and infrastructure decline (i.e., counter-urbanization) can support a greater diversity of host species and a larger and more diverse pool of pathogens. We did so by characterizing pathogenic Leptospira infection relative to rodent host richness and abundance across a mosaic of abandonment in post-Katrina New Orleans (Louisiana, USA). We found that Leptospira infection loads were highest in areas that harboured increased rodent species richness (which ranged from one to four rodent species detected). Areas with greater host co-occurrence also harboured a greater abundance of hosts, including the host species most likely to carry high infection loads, indicating that Leptospira infection can be amplified by increases in overall and relative host abundance. Evidence of shared infection among rodent host species indicates that cross-species transmission of Leptospira probably increases infection at sites with greater host richness. Additionally, evidence that rodent co-occurrence and abundance and Leptospira infection load parallel abandonment suggests that counter-urbanization can elevate zoonotic disease risk within cities, particularly in underserved communities that are burdened with disproportionate concentrations of derelict properties.

The prevalence and risk factors associated with Leptospira in donkeys in Ngaka Modiri Molema District, North West Province, South Africa

Background and Aim:

Leptospirosis is one of the major emerging global economic and health problems affecting donkeys, thereby reducing their work output. Furthermore, the disease has public health importance because of its zoonotic nature. Despite the significant contribution donkeys make to the national economy, less attention is given to diseases that afflict donkeys and reduce their productivity and performance. A cross-sectional study was conducted to investigate the seroprevalence of Leptospira and identify risk factors associated with the occurrence of the disease among donkeys in the study area.

Materials and Methods:

A questionnaire survey was used to collect the following data: Demographic, environmental, management, and health-related factors. Blood samples were aseptically collected from 365 randomly selected donkeys from 19 villages. The sera were tested using the microscopic agglutination test. Categorical variables were summarized and presented as proportions and their 95% confidence interval (CI). A binary logistic regression model was fitted to the data to identify risk factors associated with Leptospira seroprevalence in donkeys within the study areas.

Results:

The majority of the donkeys (29.6%; n=108/365) were from Mafikeng local municipality, and the rest (19.7%; n=72/365) were from Ratlou. Just over half (58.1%; n=212/365) of the donkeys tested were female, and the remaining (41.9%; n=153/365) were males. In addition, most donkeys (42.7%; n=156/365) were between 6 and 12 years old, followed by those between 0 and 5 years (37%; n=135/365), and only 20.3% (n=74/365) were above 12 years. Out of the donkeys tested, 11.5% (95% CI: 4.86-18.14) donkeys tested positive for Leptospira antibodies. The most common serovar was Bratislava (81%; n=34/42), followed by Tarassovi (19.04%; n=8/42). While gender was positively associated with seroprevalence of the disease (Adjusted Odds Ratio [AOR]=4.88; p=0.0001), the presence of horses (AOR=0.226; p=0.002) and agricultural activities (AOR=0.093; p=0.0001) in the vicinity of the dwellings of the donkeys were negatively associated with Leptospira seropositivity in the study area.

Conclusion:

Findings reported here show that donkeys in the study area are reservoirs for the predominant serovar Bratislava and the less dominant serovar Tarassovi. The gender of the donkey was a risk factor for Leptospira seroprevalence. Further studies are needed to investigate the role of agricultural activities in the vicinity of the dwellings of donkeys on the occurrence of Leptospira in the study area.

Understanding leptospirosis eco-epidemiology by environmental DNA metabarcoding of irrigation water from two agro-ecological regions of Sri Lanka

Background

Leptospirosis is one of the most significant zoonoses across the world not only because of its impact on human and animal health but also because of the economic and social impact on agrarian communities. Leptospirosis is endemic in Sri Lanka where paddy farming activities, the use of draught animals in agriculture, and peridomestic animals in urban and rural areas play important roles in maintaining the infection cycle of pathogenic Leptospira, especially concerning animals as a potential reservoir. In this study, an environmental DNA (eDNA) metabarcoding methodology was applied in two different agro-ecological regions of Sri Lanka to understand the eco-epidemiology of leptospirosis.

Methodology/Principal findings

Irrigation water samples were collected in Kandy District (wet zone mid-country region 2) and Girandurukotte, Badulla District (intermediate zone low-country region 2); and analysed for the presence of pathogenic Leptospira, associated microbiome and the potential reservoir animals. Briefly, we generated PCR products for high-throughput sequencing of multiple amplicons through next-generation sequencing. The analysis of eDNA showed different environmental microbiomes in both regions and a higher diversity of Leptospira species circulating in Kandy than in Girandurukotte. Moreover, the number of sequence reads of pathogenic Leptospira species associated with clinical cases such as L. interrogans was higher in Kandy than in Girandurukotte. Kandy also showed more animal species associated with pathogenic bacterial species than Girandurukotte. Finally, several pathogenic bacterial species including Arcobacter cryaerophilus, responsible for abortion in animals, was shown to be associated with pathogenic Leptospira.

Conclusions/Significance

Leptospirosis has been considered to be endemic in wet regions, consistently, leptospiral sequences were detected strongly in Kandy. The great Leptospira species diversity in Kandy observed in this study shows that the etiological agents of leptospirosis in Sri Lanka might be underestimated. Furthermore, our eDNA metabarcoding can be used to discriminate bacterial and animal species diversity in different regions and to explore environmental microbiomes to identify other associated bacterial pathogens in the environment.

Leptospirosis is a widespread bacterial zoonosis with increasing importance due to its vast range of reservoir hosts. Early symptoms are shared by other infectious diseases common in tropical and sub-tropical regions, where the real burden and risk factors need to be known. In Sri Lanka, leptospirosis is mostly an occupational disease associated with freshwater or animal exposure in agriculture communities. Thus, there is a need for understanding the epidemiology of leptospirosis in agrarian regions of the country for developing better prevention and intervention strategies. In this study, we applied an environmental DNA metabarcoding methodology to understand the environmental microbiome, potential reservoir animals and the Leptospira species circulating in two different agro-ecological regions of Sri Lanka: Kandy (wet region mid-country region 2) and Girandurukotte (intermediate region low-country region 2). It is known that pathogenic Leptospira are excreted through the urine of reservoir animals in the environment, where they can persist in humid conditions. Congruently, this study showed a higher detection of pathogenic Leptospira in the environment of Kandy where the environmental microbiome showed a higher diversity than Girandurukotte. Potential animal reservoirs were also detected in samples positive for pathogenic Leptospira, suggesting that environmental DNA metabarcoding can provide important information for management and intervention strategies to control leptospirosis.

Leptospira transport medium (LTM): A practical tool for leptospires isolation

The isolation of Leptospira is challenging, since the bacteria of this genus are susceptible to adverse environmental conditions and may not remain viable for extend periods in urine samples. This study attempted to develop and evaluate a simple and practical method to isolate leptospires from bovine urine samples. A culture medium for sample transport, named Leptospira Transport Medium (LTM), was described and validated using reference serovars of Leptospira spp. in addition to autochthonous strains isolated in Brazil. We evaluated LTM in the field, by collecting 215 urine samples from slaughtered cattle and immediately seeding them in LTM and Fletcher's medium, used as control. The cultures were sent to a laboratory within 10 days for further processing. Moreover, 16S PCR was also performed on the urine samples directly to detect Leptospira DNA. Using LTM enabled 52 isolates (24.2%) to be obtained in pure culture, and contamination was only observed in 15/215 samples (7.0%). Regarding the samples in Fletcher's medium, 10 (4.6%) isolates were obtained. With 16S PCR performed in the urine samples, 31 samples (14.4%) were determined to be positive. LTM was developed and used in a simple and practical way and can significantly improve the isolation of leptospires from urine samples, as well as being highly useful in remote areas, not only in Brazil but also in other countries where few easily accessible laboratories are available. Furthermore, LTM can be prepared by laboratories and provided to veterinarians and technicians for urine collection in the field.

Poly(diaminosulfide) Microparticle-Based Vaccine for Delivery of Leptospiral Antigens

Leptospirosis is a debilitating infectious disease that detrimentally affects both animals and humans; therefore, disease prevention has become a high priority to avoid high incidence rates of disease in the herd and break the transmission cycle to humans. Thus, there remains an important unmet need for a prophylactic vaccine that can provide long-term immunity against leptospirosis in cattle. Herein, a novel vaccine formulation was developed where poly(diaminosulfide) polymer was employed to fabricate microparticles encapsulating the antigen of Leptospira borgpetersenii serovar Hardjo strain HB15B203 (L203-PNSN). A prime-boost vaccination with a L203-PNSN microparticle formulation increased the population of L203-specific CD3⁺ T cells and CD21⁺ B cells to levels that were significantly higher than those of cattle vaccinated with L203-AlOH or the vehicle control (empty PNSN microparticles and blank AlOH). In addition, L203-PNSN was demonstrated to stimulate durable humoral immune responses as evidenced by the increases in the antibody serum titers following the vaccination. It was also found that cattle vaccinated with L203-PNSN produced higher macroscopic agglutinating titers than cattle in other groups. Thus, it can be concluded that L203-PNSN is a novel first-in-class microparticle-based Leptospira vaccine that represents a powerful platform with the potential to serve as a prophylactic vaccine against leptospiral infection in cattle.

The correlation between local weather and leptospirosis incidence in Kandy district, Sri Lanka from 2006 to 2015

Background: Leptospirosis is an important public health problem in Sri Lanka. Most people become infected by contact with leptospires in soil and in surface water. Survival of leptospires in the environment depends upon the moisture in soil, humidity, temperature and surface water. Leptospires are spread by flood water and waterways. Therefore, the weather of an area influences the leptospirosis incidence of that area. Objectives: To find out the correlations between the leptospirosis incidence in the district of Kandy, Sri Lanka, and local weather variables and then to explore the utility of the findings. Methods: We gathered data on reported leptospirosis cases in the Kandy district and mid-year population data and calculated weekly incidences for 2006 to 2015. Daily weather data from Katugastota weather station was obtained and converted into weekly data. We plotted time series graphs and observed the correlation between six aggregated weather parameters and leptospirosis incidence. Those weather parameters were rainfall, the count of wet days per week, days with rainfall >100 mm per week, minimum temperature, average temperature and average humidity. Then we looked for correlations between leptospirosis incidence and those weather parameters by performing the wavelet analysis. Results: Our wavelet analysis results show peaks of wet days per week, days with rainfall >100 mm per week, minimum temperature, average temperature and average humidity respectively after 2, 3, 13, 20 and 1 week lags were followed by peaks of leptospirosis incidence. Nadirs (troughs) of rainfall after a week were followed by nadirs of leptospirosis incidence. Conclusions: All weather parameters studied are correlated with local leptospirosis incidence and the climate in Kandy is conducive for leptospirosis transmission. Leptospirosis incidence in the Kandy district is high compared to the national and global incidence. Therefore, leptospirosis preventive work in Kandy deserves more attention, especially during months with favorable weather for leptospirosis transmission. Video abstract Read the transcript Watch the video on Vimeo.

Identification of Leptospira spp. from environmental sources in areas with high human leptospirosis incidence in the Philippines

Leptospira is the causative agent of leptospirosis, which is considered an emerging major threat to public health due to its increasing frequency reported worldwide. In the Philippines, the prevalence of the disease continuously rises, particularly in urban areas. Because leptospirosis is commonly transmitted through contact with contaminated environment, water and soil samples were collected in regions in the Philippines where high incidence of human leptospirosis cases was reported recently. Of the 54 samples screened for the presence of Leptospira, 35% were found positive through 23S rRNA gene PCR-based detection. None were found positive when primers targeting lipL32, lipL41, and ompL1 genes were used. Most of these isolates were collected from rural areas. However, 16S rRNA gene sequencing identified all isolates to be L. yanagawae and L. meyeri, which are nonpathogenic. Despite the lack of evidence of the presence of pathogenic species in the environmental sources, the results still suggest that leptospires persist in these areas. These data are crucial for environmental monitoring and identification of contaminated areas where humans may be at risk of infection.

Whole cell matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for identification of Leptospira spp. in Thailand and Lao PDR

Leptospirosis is a zoonosis with a worldwide distribution, caused by pathogenic spirochetes of the genus Leptospira. The classification and identification of leptospires can be conducted by both genotyping and serotyping which are time-consuming and established in few reference laboratories. This study used matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) as rapid and accurate tool for the identification of leptospires. The whole cell protein spectra of 116 Leptospira isolates including 15 references Leptospira spp. (pathogenic, n = 8; intermediate, n = 2; non-pathogenic, n = 5) and 101 Leptospira spp. clinical isolates was created as an in-house MALDI-TOF MS database. Ninety-seven clinical isolates from Thailand and Laos was validated with these protein spectra and revealed 98.9% correct identification when compared with 16S rRNA gene sequences method. Moreover, MALDI-TOF MS could identify spiked leptospires whole cell in urine. Biomarkers for differentiation of leptospires phylogeny and specific protein spectra for most found Leptospira spp. in this area (L. interrogans, L. kirschneri, L. borgpetersenii) based on MALDI-MS algorithm were demonstrated.

Prospective study of canine leptospirosis in shelter and stray dog populations: Identification of chronic carriers and different Leptospira species infecting dogs

Dogs are highly susceptible to the leptospiral infection, notably stray and sheltered dogs. Unsanitary conditions often observed in dog shelters may predispose the introduction and spread of leptospires among sheltered populations, potentially increasing the chances for the inadvertent adoption of asymptomatically infected animals. The present work describes a longitudinal study using a multidisciplinary approach for the identification of chronically infected dogs and the characterization of potentially pathogenic strains circulating among stray and sheltered dog populations in São Paulo, Brazil. A total of 123 dogs from three populations were included. The initial evaluation consisted of blood and urine quantitative PCR testing (qPCR), the detection of specific antibodies by microscopic agglutination test (MAT), physical examination and hematological and serum biochemistry analyses. The qPCR-positive dogs were prospectively examined, and reevaluations also included culture from urine samples. Positive qPCR samples were subjected to 16S rRNA and secY gene phylogenetic analysis. The recovered strains were characterized by Multilocus Sequence Typing, polyclonal serogroup identification and virulence determination. Leptospiruria was detected in all populations studied (13/123), and phylogenetic analysis revealed that 10 dogs had L. interrogans infection. Three dogs (3/13) had L. santarosai infection. The secY phylogenetic analysis revealed that the L. santarosai sequences clustered separately from those obtained from other hosts. Ten leptospiruric dogs were reevaluated, and three dogs presented persistent leptospiruria, allowing culturing from two dogs. The strains were characterized as L. interrogans serogroup Canicola (virulent) and L. santarosai serogroup Sejroe (not virulent). Serum samples were retested by MAT using the DU92 and DU114 strains as antigens, and no increased seroreactivity was detected. Asymptomatic L. santarosai infection was observed in all populations studied, suggesting a possible role of dogs in the chain of transmission of this leptospiral species. The results suggest a genetic distinction between lineages of Brazilian L. santarosai maintained by dogs and other animal hosts. Our findings revealed that dogs could act as maintenance hosts for distinct pathogenic Leptospira, highlighting also that asymptomatically infected dogs can be inadvertently admitted and adopted in dog shelters, potentially increasing the risks of zoonotic transmission.

Continuous Excretion of Leptospira borgpetersenii Ballum in Mice Assessed by Viability Quantitative Polymerase Chain Reaction

Rodents are the main reservoir animals of leptospirosis. In this study, we characterized and quantified the urinary excretion dynamics of Leptospira by Mus musculus infected with 2 × 108 virulent Leptospira borgpetersenii serogroup Ballum. Each micturition was collected separately in metabolic cages, at 12 time points from 7 to 117 days post-infection (dpi). We detected Leptospira in all urine samples collected (up to 8 per time point per mouse) proving that Leptospira excretion is continuous with ca. 90% live L. borgpetersenii Ballum, revealed by viability quantitative polymerase chain reaction. Microscopic visualization by Live/Dead fluorescence confirmed this high proportion of live bacteria and demonstrated that L. borgpetersenii Ballum are excreted, at least partly, as bacterial aggregates. We observed two distinct phases in the excretion dynamics, first an increase in Leptospira concentration shed in the urine between 7 and 63 dpi followed by a plateau phase from 63 dpi onward, with up to 3 × 107Leptospira per mL of urine. These two phases seem to correspond to progressive colonization of renal tubules first, then to stable cell survival and maintenance in kidneys. Therefore, chronically infected adult mice are able to contaminate the environment via urine at each micturition event throughout their lifetime. Because Leptospira excretion reached its maximum 2 months after infection, older rodents have a greater risk of contaminating their surrounding environment.

Critical Knowledge Gaps in Our Understanding of Environmental Cycling and Transmission of Leptospira spp

Exposure to soil or water contaminated with the urine of Leptospira-infected animals is the most common way in which humans contract leptospirosis. Entire populations can be at high risk of leptospirosis while working in inundated fields, when engaging in aquatic sports, or after periods of heavy rainfall. The risk of infection after contact with these environmental sources depends on the ability of Leptospira bacteria to survive, persist, and infect new hosts. Multiple variables such as soil and water pH, temperature, and even environmental microbial communities are likely to shape the environmental conditions needed by the pathogen to persist. Here we review what is known about the environmental phase of the infectious Leptospira transmission cycle and identify knowledge gaps that will serve as a guide for future research.